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Investigation and analysis of taxonomic irregularities with the Botryosphaeriaceae

Sakalidis, Monique (2011) Investigation and analysis of taxonomic irregularities with the Botryosphaeriaceae. PhD thesis, Murdoch University.

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      Abstract

      Many members of Botryosphaeriaceae live as endophytes with a latent phase that can cause disease in native and non-native plant hosts around the world. The main Botryosphaeriaceae examined in this thesis included species in the Lasiodiplodia theobromae species complex, Neofusicoccum parvum-ribis species complex and Neofusicoccum australe. A combination of traditional morphology, pathogenicity trials, multiple gene phylogenies and microsatellite analyses were used to probe between and within species.

      Within native bushland in the Kimberley, Western Australia, 13 taxa of the Botryosphaeriaceae were identified; Lasiodiplodia mahajangana was the most common species and was confirmed as a potentially significant pathogen of Adansonia gregorii. These fungi also colonised non-native Mangifera indica in the same region possibly displacing the exotic microflora of M. indica. Pathogenicity tests resulted in lesion development of mango fruit and excised stems.

      Isolates in the N. parvum- ribis complex collected from eucalypt cankers in eastern Australia exhibited overlapping morphology and pathogenicity. Phylogenetic analysis of four gene regions and application of the Genealogical Sorting Index to the same data set supported two new species. Consequently, the description of Neofusicoccum occulatum is presented. Neofusicoccum parvum has been recorded in 71 host species across six continents and 21 countries. Population data analysis of N. parvum populations reflects admixture and repeat introductions of new genetic material. No specific host associations were observed.

      Evaluation of EF1-α molecular data amongst members of L. theobromae species complex suggests there are an additional four taxa and two potential hybrids. The 19 Lasiodiplodia taxa have been recorded in 56 host species, across six continents and 23 countries. Nine Lasiodiplodia taxa and one hybrid have been identified in Australia. Population analysis suggests the Kimberley populations are sexually reproducing with no discernable host restriction and display moderate genetic diversity.

      Neofusicoccum australe is found across nine countries and 46 host species. Phylogenetic analysis of the ITSrDNA sequence identified a single dominant ITS haplotype found in most locations and another 12 rare to moderately rare haplotypes found in one to two locations. Using microsatellite markers, populations of N. australe were found to be highly diverse and there was no discernable host or habitat restriction. The dominance of N. australe in native forest throughout the southwest of Western Australia suggests that this species is endemic to this area.

      The species studied in this thesis appear to be capable latent pathogens with no obvious restriction to host colonisation or habitat. Multiple species and multiple genotypes of one species can colonise small sections of a single host. Cryptic sympatric speciation is common despite no observable telomorphs. These species appear to be highly competitive and their endophytic life strategy appears to provide effective means for dissemination via asymptomatic host tissue, which could complicate quarantine efforts that typically rely on the visual presence of disease symptoms.

      Publication Type: Thesis (PhD)
      Murdoch Affiliation: School of Biological Sciences and Biotechnology
      Supervisor: Burgess, Treena and Hardy, Giles
      URI: http://researchrepository.murdoch.edu.au/id/eprint/5800
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